685 research outputs found
Dependency of halo concentration on mass, redshift and fossilness in Magneticum hydrodynamic simulations
We study the dependency of the concentration on mass and redshift using three
large N-body cosmological hydrodynamic simulations carried out by the
Magneticum project. We constrain the slope of the mass-concentration relation
with an unprecedented mass range for hydrodynamic simulations and find a
negative trend on the mass-concentration plane and a slightly negative redshift
dependency, in agreement with observations and other numerical works. We also
show how the concentration correlates with the fossil parameter, defined as the
stellar mass ratio between the central galaxy and the most massive satellite,
in agreement with observations. We find that haloes with high fossil parameter
have systematically higher concentration and investigate the cause in two
different ways. First we study the evolution of haloes that lives unperturbed
for a long period of time, where we find that the internal region keeps
accreting satellites as the fossil parameter increases and the scale radius
decreases (which increases the concentration). We also study the dependency of
the concentration on the virial ratio and the energy term from the surface
pressure . We conclude that fossil objects have higher concentration
because they are dynamically relaxed, with no in-fall/out-fall material and had
time to accrete their satellites.Comment: 13 pages, 10 figure
Pàncrees : ultrasons per a un millor diagnòstic
Les tècniques no invasives són essencials en medicina per al diagnòstic de malalties. Una d'aquestes tècniques és la ultrasonografia, una tècnica d'exploració que registra els ecos d'ones acústiques a l'interior del cos. Una de les aplicacions dels ultrasons és l'exploració del pàncrees.Las técnicas no invasivas son esenciales en medicina para el diagnóstico de enfermedades. Una de estas técnicas es la ultrasonografía, una técnica de exploración que registra los ecos de ondas acústicas en el interior del cuerpo. Una de las aplicaciones de los ultrasonidos es la exploración del páncreas.Non invasive techniques are essential for diagnosis in medicine. One of these techniques is the ultrasonography, an exploration technique that registers the echoes of acoustic waves inside the body. One of the applications of the ultrasounds is the exploration of the pancreas
Heat flows and energetic behavior of a telecommunication radio base station
This paper shows a study on energetic consumption of BTSs (Base Transceiver
Stations) for mobile communication, related to conditioning functions. An
energetic "thermal model" of a telecommunication station is proposed and
studied. The results have been validated with a BTS in central Italy, showing
good agreement. Findings show a substantial high internal-external temperature
difference in the containing shelter, particularly during daytime and warm
months, due to sources of heat (equipment, external temperature and sun
radiation) and to the difficulty in spread the warmth out. The necessity to
keep the operating temperatures within a given range for the correct
functioning of the electronic equipment requires the use of conditioning
setups, and this significantly increases the energetic demand of the whole
system. The analysis of thermal flows across the shelter can help to gather
further data on its temperature behavior and to devise practical measures to
lower the power demand, while keeping the operating parameters in the suggested
ranges. The investigation of some operating parameters of the equipment and of
the shelter, such as threshold set-points, air vent area, external wall
transmittance and reflectivity, suggests annual energy savings between 10% and
30%.Comment: 18 pages, 12 figure
Study of 222−220Rn Measurement Systems Based on Electrostatic Collection by Using Geant4+COMSOL Simulation
Using Monte Carlo (with Geant4) and COMSOL simulations, the authors have defined a useful tool to reproduce the alpha spectroscopy of 222Rn, 220Rn and their ionized daughters by measurement systems based on electrostatic collection on a silicon detector, inside a metallic chamber. Several applications have been performed: (i) simulating commercial devices worldwide used, and comparing them with experimental theoretical results; (ii) studying of realization of new measurement systems through investigation of the detection efficiency versus different chamber geometries. New considerations and steps forward have been drawn. The present work is a novelty in the literature concerning this research framework
Structural and dynamical modeling of WINGS clusters. I. The distribution of cluster galaxies of different morphological classes within regular and irregular clusters
[Abridged] We use the WINGS database to select a sample of 67 nearby galaxy
clusters with at least 30 spectroscopic members each. 53 of these clusters do
not show evidence of substructures in phase-space, while 14 do. We estimate the
virial radii and circular velocities of the 67 clusters by a variety of proxies
(velocity dispersion, X-ray temperature, and richness) and use these estimates
to build stack samples from these 53 and 14 clusters ('Reg' and 'Irr' stacks,
respectively). We determine the number-density and velocity-dispersion profiles
(VDPs) of E, S0, and Sp+Irr (S) galaxies in the Reg and Irr samples,
separately, and fit models to these profiles. The number density profiles of E,
S0, and S galaxies are adequately described by either a NFW or a cored King
model, both for the Reg and Irr samples, with a slight preference for the NFW
model. The spatial distribution concentration increases from the S to the S0
and to the E populations, both in the Reg and the Irr stacks, reflecting the
well-known morphology-radius relation. Reg clusters have a more concentrated
spatial distribution of E and S0 galaxies than Irr clusters, while the spatial
distributions of S galaxies in Reg and Irr clusters are similar. We propose a
new phenomenological model that provides acceptable fits to the VDP of all our
galaxy samples. The VDPs become steeper and with a higher normalization from E
to S0 to S galaxies. The S0 VDP is close to that of E galaxies in Reg clusters,
and intermediate between those of E and S galaxies in Irr clusters. Our results
suggest that S galaxies are a recently accreted cluster population, that take
less than 3 Gyr to evolve into S0 galaxies after accretion, and in doing so
modify their phase-space distribution, approaching that of cluster ellipticals.
While in Reg clusters this evolutionary process is mostly completed, it is
still ongoing in Irr clusters.Comment: A&A, in press - 11 pages, 9 figures, 4 table
Cardiac fluid dynamics anticipates heart adaptation
Hemodynamic forces represent an epigenetic factor during heart development and are supposed to influence the pathology of the grown heart. Cardiac blood motion is characterized by a vortical dynamics, and it is common belief that the cardiac vortex has a role in disease progressions or regression. Here we provide a preliminary demonstration about the relevance of maladaptive intra-cardiac vortex dynamics in the geometrical adaptation of the dysfunctional heart. We employed an in vivo model of patients who present a stable normal heart function in virtue of the cardiac resynchronization therapy (CRT, bi-ventricular pace-maker) and who are expected to develop left ventricle remodeling if pace-maker was switched off. Intra-ventricular fluid dynamics is analyzed by echocardiography (Echo-PIV). Under normal conditions, the flow presents a longitudinal alignment of the intraventricular hemodynamic forces. When pacing is temporarily switched off, flow forces develop a misalignment hammering onto lateral walls, despite no other electro-mechanical change is noticed. Hemodynamic forces result to be the first event that evokes a physiological activity anticipating cardiac changes and could help in the prediction of longer term heart adaptations
Left ventricular pacing vector selection by novel echo-particle imaging velocimetry analysis for optimization of quadripolar cardiac resynchronization device: A case report
Background: The availability of pacing configurations offered by quadripolar left ventricular leads could improve patients\u2019 response to cardiac resynchronization therapy; however, the selection of an optimal setting remains a
challenge. Echo-particle imaging velocimetry has shown that regional anomalies of synchrony/synergy of the left ventricle are related to the alteration, reduction, or suppression of the physiological intracavitary pressure gradients.
These observations are also supported by several numerical models of the left ventricle that have shown the close relationship between wall motion abnormalities, change of intraventricular flow dynamics, and abnormal
distribution of forces operating on the ventricular endocardium.
Case presentation: A 73-year-old white man in New York Heart Association III functional class with an ejection fraction of 27.5 % did not improve after 1 month of cardiac resynchronization therapy. Five configurations were
tested and settings were defined by optimizing intraventricular flow. After 6 months, he became New York Heart Association II class with left ventricular ejection fraction of 53.2 %.
Conclusions: The abnormal dynamic of pressure gradients during the cardiac cycle, through biohumoral endocrine, autocrine, and paracrine transduction, may lead to structural changes of the myocardial walls with subsequent left ventricular remodeling. The echo-particle imaging velocimetry technique may be useful for elucidating the favorable effects of cardiac resynchronization therapy on intraventricular fluid dynamics and it could be used to identify appropriate pacing setting during acute echocardiographic optimization of left pacing vector
Changes in electrical activation modify the orientation of left ventricular flow momentum: novel observations using echocardiographic particle image velocimetry
Changes in electrical activation sequence are known to affect the timing of cardiac mechanical events. We aim to demonstrate that these also modify global properties of the intraventricular blood flow pattern. We also explore whether such global changes present a relationship with clinical outcome
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